Studies on the synthesis of pentacyclic strychnos indole alkaloids. photocyclization of n-chloroacetyl-1,2,3,4,5,6-hexahydro-1,5-methanoazocino[4,3-b]indole derivatives

Photocyclization of 2-chloroacetyl-1,2,3,4,5,6-hexahydro-1, 5-methanoazocino[4,3-b]indole ($\text{5}$) takes place at the indole 4-position to give a 1 ,2 ,3 ,4 , 5 ,6-hexahydro-2 ,11-ethano-1 ,5-methanoazocino [4 , 3-6] indole system. Consequently, the method appears to be unsuitable for constructing the pyrrolidine ring of pentacyclic Strychnos indole alkaloids.     

Particle-particle particle-mesh method for dipolar interactions: on error estimates and efficiency of schemes with analytical differentiation and mesh interlacing

The interlaced and non-interlaced versions of the dipolar particle-particle particle-mesh (P(3)M) method implemented using the analytic differentiation scheme (AD-P(3)M) are presented together with their respective error estimates for the calculation of the forces, torques, and energies. Expressions for the optimized lattice Green functions, and for the Madelung self-forces, self-torques and self-energies are given. The applicability of the theoretical error estimates are thoroughly tested and confirmed in several numerical examples. Our results show that the accuracy of the calculations can be improved substantially when the approximate (mesh computed) Madelung self-interactions are subtracted. Furthermore, we show that the interlaced dipolar AD-P(3)M method delivers a significantly higher accuracy (which corresponds approximately to using a twice finer mesh) than the conventional method, allowing thereby to reduce the mesh size with respect to the non-interlaced version for a given accuracy. In addition, we present similar expressions for the dipolar ik-differentiation interlaced scheme, and we perform a comparison with the AD interlaced scheme. Rough tests for the relative speed of the dipolar P(3)M method using ik-differentiation and the interlaced/non-interlaced AD schemes show that when FFT computing time is the bottleneck, usually when working at high precisions, the interlaced AD-scheme can be several times faster than the other two schemes. For calculations with a low accuracy requirement, the interlaced version can perform worse than the ik and the non-interlaced AD schemes.     

Photoacclimation in spathiphyllum

We studied photoacclimation in Spathiphyllum grown at an irradiance of 40 or 420 micromol/m2 s (LL or HL, respectively). All parameters studied responded to acclimation. Leaves at LL, in contrast to HL, were thinner and oriented perpendicular to the incident light, had more chlorophyll per g f w, fewer stomata on the upper leaf surface and a reduced layer of mesophyll cells. Their chloroplasts at HL had wider grana with less thylakoids per granum, and better organized photosystems than at LL. PSI and PSII activities per mg chlorophyll ( Vmax ), and PSI and PSII content (total activity per g f w), were lower at LL than at HL and so was the light requirement for saturation of the PSI or PSII partial photoreactions, suggesting that fewer photosystems with larger antenna size prevail at LL, but many more with smaller antenna size at HL. Analysis of chlorophyll distribution among the thylakoid pigment-protein complexes showed less antenna chlorophyll serving PSII (CPa+LHCP1+LHCP3) than that serving PSI (CPIa+CPI+LHCP2) at LL as compared to HL, and thus a lower PSII/PSI ratio at LL, in agreement with the general finding that LL plants, with larger PSII antenna size, have lower PSII/PSI ratio. The increase in PSI antenna size at LL was correlated with the increase in the distribution of chlorophyll in pigment-protein complexes serving PSI, and a very large chlorophyll/protein molar ratio in the isolated CPI complex. On the other hand, the PSII antenna chlorophyll (CPa+LHCP1+LHCP3) on a g f w basis, and the chlorophyll a/b ratio remained more or less constant at LL or HL. This may reflect our finding that Spathiphyllum contains mainly the 27 kDa inner LHCII antenna protein, the size of which remains unaffected by photoacclimation. The increase in the distribution of chlorophyll in pigment-protein complexes serving PSII at HL, therefore, reflects the higher population of PSII at HL. Very high PSI activity was found at HL, which we attribute to the highly organized small in size PSI.     

Theoretical insights into the ferromagnetic coupling in oxalato-bridged chromium(III)-cobalt(II) and chromium(III)-manganese(II) dinuclear complexes with aromatic diimine ligands

Two novel heterobimetallic complexes of formula [Cr(bpy)(ox)(2)Co(Me(2)phen)(H(2)O)(2)][Cr(bpy)(ox)(2)]·4H(2)O (1) and [Cr(phen)(ox)(2)Mn(phen)(H(2)O)(2)][Cr(phen)(ox)(2)]·H(2)O (2) (bpy = 2,2'-bipyridine, phen = 1,10-phenanthroline, and Me(2)phen = 2,9-dimethyl-1,10-phenanthroline) have been obtained through the "complex-as-ligand/complex-as-metal" strategy by using Ph(4)P[CrL(ox)(2)]·H(2)O (L = bpy and phen) and [ML'(H(2)O)(4)](NO(3))(2) (M = Co and Mn; L' = phen and Me(2)phen) as precursors. The X-ray crystal structures of 1 and 2 consist of bis(oxalato)chromate(III) mononuclear anions, [Cr(III)L(ox)(2)](-), and oxalato-bridged chromium(III)-cobalt(II) and chromium(III)-manganese(II) dinuclear cations, [Cr(III)L(ox)(μ-ox)M(II)L'(H(2)O)(2)](+)[M = Co, L = bpy, and L' = Me(2)phen (1); M = Mn and L = L' = phen (2)]. These oxalato-bridged Cr(III)M(II) dinuclear cationic entities of 1 and 2 result from the coordination of a [Cr(III)L(ox)(2)](-) unit through one of its two oxalato groups toward a [M(II)L'(H(2)O)(2)](2+) moiety with either a trans- (M = Co) or a cis-diaqua (M = Mn) configuration. The two distinct Cr(III) ions in 1 and 2 adopt a similar trigonally compressed octahedral geometry, while the high-spin M(II) ions exhibit an axially (M = Co) or trigonally compressed (M = Mn) octahedral geometry in 1 and 2, respectively. Variable temperature (2.0-300 K) magnetic susceptibility and variable-field (0-5.0 T) magnetization measurements for 1 and 2 reveal the presence of weak intramolecular ferromagnetic interactions between the Cr(III) (S(Cr) = 3/2) ion and the high-spin Co(II) (S(Co) = 3/2) or Mn(II) (S(Mn) = 5/2) ions across the oxalato bridge within the Cr(III)M(II) dinuclear cationic entities (M = Co and Mn) [J = +2.2 (1) and +1.2 cm(-1) (2); H = -JS(Cr)·S(M)]. Density functional electronic structure calculations for 1 and 2 support the occurrence of S = 3 Cr(III)Co(II) and S = 4 Cr(III)Mn(II) ground spin states, respectively. A simple molecular orbital analysis of the electron exchange mechanism suggests a subtle competition between individual ferro- and antiferromagnetic contributions through the σ- and/or π-type pathways of the oxalato bridge, mainly involving the d(yz)(Cr)/d(xy)(M), d(xz)(Cr)/d(xy)(M), d(x(2)-y(2))(Cr)/d(xy)(M), d(yz)(Cr)/d(xz)(M), and d(xz)(Cr)/d(yz)(M) pairs of orthogonal magnetic orbitals and the d(x(2)-y(2))(Cr)/d(x(2)-y(2))(M), d(xz)(Cr)/d(xz)(M), and d(yz)(Cr)/d(yz)(M) pairs of nonorthogonal magnetic orbitals, which would be ultimately responsible for the relative magnitude of the overall ferromagnetic coupling in 1 and 2.     

End-to-end single cyanato and thiocyanato bridged Cu(II) polymers with a new tridentate Schiff base ligand: crystal structure and magnetic properties

A new tridentate Schiff base ligand HL (L = C14H19N2O), derived from the condensation of benzoylacetone and 2-dimethylaminoethylamine in a 1:1 ratio, reacts with copper(ii) acetate and cyanate, thiocyanate or azide, to give rise to several end-to-end polymeric complexes of formulae [CuL(mu(1,3)-NCO)]n 1, [CuL(mu(1,3)-NCS)]n 2 and the complex 3 has two crystallographically independent units of formula [CuL(N3)] in the asymmetric unit cell. Complex 3 exists in dimeric form rather than as a polymeric chain. Compound 1 is the first report of a singly end-to-end cyanate bridged polymeric chain of Cu(II) with a Schiff base as a co-ligand. There are many examples of double NCS bridged polymeric chains, but fewer singly bridged ones such as compound 2. We have characterized these complexes by analytical, spectroscopic, structural and variable temperature magnetic susceptibility measurements. The coordination geometry around the Cu(II) centers is distorted square pyramidal for 1 and 2 and square planar for complex 3. The magnetic susceptibility data show slight antiferromagnetic coupling for the polymers having J values -0.19 and -0.57 cm(-1) for complexes 1 and 2 respectively. The low values of J are consistent with the equatorial-axial disposition of the bridges in the polymers.     

Aggregation of [Cu(II)4] building blocks into [Cu(II)8] clusters or a [Cu(II)4]infinity chain through subtle chemical control

Coordination complexes of the ligand H3L [1,3-bis(3-oxo-3-phenylpropionyl)-2-hydroxy-5-methylbenzene] with Cu(II) are reported. Clusters showing various nuclearities or modes of supramolecular organization have been prepared by slightly changing the reaction conditions and have been crystallographically characterized. The reaction of H3L with one equivalent of Cu(OAc)2 in DMF yields the dinuclear complex [Cu2(HL)2(dmf)2] (1). Reaction in MeOH of H3L with an increased amount of metal, in the form of Cu(NO3)2, and excess strong base (nBu4NOH) affords the cluster [Cu8(L)2(OMe)8(NO3)2] (2). Complex 2 is a dimer of two linear [Cu4] arrays bridged by methoxide ligands, where the polynucleating ligand is fully deprotonated. The [Cu4]2 clusters are linked to each other by NO3- bridges to form one-dimensional coordination polymers. The link between [Cu8] units and their relative spatial positioning can be modified by changing the anion of the Cu(II) salt, as demonstrated by the synthesis of the cluster polymers [Cu8(L)2(OMe)8Cl2] (3) and [Cu8(L)(OMe)7.86Br2.14] (4), where only NO3- has been replaced by Cl- or Br-, respectively. Similarly, when ClO4- is used, compound [Cu8(L)2(OMe)8(ClO4)2(MeOH)4] (5) can be isolated. It contains independent [Cu8] units. A slight change in the stoichiometry of the reaction leading to 2 affords the related complex catena-[Cu4(L)(OMe)3(NO3)2(H2O)0.36] (6). This polymer contains essentially the same [Cu4] moiety as 2, albeit organized in a completely different arrangement. Each [Cu4] unit in 6 is linked by OMe- ligands to two such equivalent groups to form an infinite chain. Magnetic susceptibility measurements reveal weak antiferromagnetic exchange between Cu(II) centers in 1 (J = -0.73 cm(-1)) and strong antiferromagnetic coupling within [Cu4] chains in 2, 5, and 6 (most negative J values of -113.8 and -177.3 cm(-1) for 2 and 6, respectively).     

Molecular-programmed self-assembly of homo- and heterometallic penta- and hexanuclear coordination compounds: synthesis, crystal structures, and magnetic properties of ladder-type CuII2MIIx (M=Cu, Ni; x=3, 4) oxamato complexes with CuII2 metallacyclophane cores

New homo- and heterometallic, hexa- and pentanuclear complexes of formula {[Cu2(mpba)2(H2O)F][Cu(Me5dien)]4}(PF6)(3).5H2O (1), {[Cu2(Me3mpba)2(H2O)2][Cu(Me5dien)]4}(ClO4)(4).12H2O (2), {[Cu2(ppba)2][Cu(Me5dien)]4}(ClO4)4 (3), and [Ni(cyclam)]{[Cu2(mpba)2][Ni(cyclam)]3}(ClO4)(4).6H2O (4) [mpba=1,3-phenylenebis(oxamate), Me3mpba=2,4,6-trimethyl-1,3-phenylenebis(oxamate), ppba=1,4-phenylenebis(oxamate), Me5dien=N,N,N'N' ',N' '-pentamethyldiethylenetriamine, and cyclam=1,4,8,11-tetraazacyclotetradecane] have been synthesized through the use of the "complex-as-ligand/complex-as-metal" strategy. The structures of 1-3 consist of cationic CuII6 entities with an overall [2x2] ladder-type architecture which is made up of two oxamato-bridged CuII3 linear units connected through two m- or p-phenylenediamidate bridges between the two central copper atoms to give a binuclear metallacyclic core of the cyclophane-type. Complex 4 consists of cationic CuII2NiII3 entities with an incomplete [2x2] ladder-type architecture which is made up of oxamato-bridged CuIINiII and CuIINiII2 linear units connected through two m-phenylenediamidate bridges between the two copper atoms to give a binuclear metallacyclophane core. The magnetic properties of 1-3 and 4 have been interpreted according to their distinct "dimer-of-trimers" and "dimer-plus-trimer" structures, respectively, (H=-J(S1A.S3A+S1A.S4A+S2B.S5B+S2B.S6B)-J'S1A.S2B). Complexes 1-4 exhibit moderate to strong antiferromagnetic coupling through the oxamate bridges (-JCu-Cu=81.3-105.9 cm-1; -JCu-Ni=111.6 cm-1) in the trinuclear and/or binuclear units. Within the binuclear metallacyclophane core, a weak to moderate ferromagnetic coupling (J'Cu-Cu=1.7-9.0 cm-1) operates through the double m-phenylenediamidate bridge, while a strong antiferromagnetic coupling (J'Cu-Cu=-120.6 cm-1) is mediated by the double p-phenylenediamidate bridge.     

Copper(II), cobalt(II), and nickel(II) complexes with a bulky anthracene-based carboxylic ligand: syntheses, crystal structures, and magnetic properties

To systematically explore the influence of the bulky aromatic ring skeleton with a large conjugated pi-system on the structures and properties of their complexes, six CuII, CoII, and NiII complexes with the anthracene-based carboxylic ligand anthracene-9-carboxylic acid (HL1), were synthesized and characterized, sometimes incorporating different auxiliary ligands: [Cu2(L1)4(CH3OH)2](CH3OH) (1), [Cu4(L1)6(L2)4](NO3)2(H2O)2 (2), {[Cu2(L1)4(L3)](CH3OH)0.25}infinity (3), [Co2(L1)4(L4)2(micro-H2O)](CH3OH) (4), {[Co(L1)2(L5)(CH3OH)2]}infinity (5), and {[Ni(L1)2(L5)(CH3OH)2]}infinity (6) (L2 = 2,2'-bipyridine, L3 = 1,4-diazabicyclo[2.2.2]octane, L4 = 1,10-phenanthroline, and L5 = 4,4'-bipyridine). 1 has a dinuclear structure that is further assembled to form a one-dimensional (1D) chain and then a two-dimensional (2D) network by the C-H...O H-bonding and pi...pi stacking interactions jointly. 2 takes a tetranuclear structure due to the existence of the chelating L2 ligand. 3 possesses a 1D chain structure by incorporating the related auxiliary ligand L3, which is further interlinked via interchain pi...pi stacking, resulting in a three-dimensional (3D) network. 4 also has a dinuclear structure and then forms a higher-dimensional supramolecular network through intermolecular pi...pi stacking and/or C-H...pi interactions. 5 and 6 are isostructural complexes, except they involve different metal ions, showing 1D chain structures, which are also assembled into 2D networks from the different crystallographic directions by interchain pi...pi stacking and C-H...pi interactions, respectively. The results reveal that the steric bulk of the anthracene ring in HL1 plays an important role in the formation of 1-6. The magnetic properties of the complexes were investigated, and the very long intermetallic distances result in weak magnetic coupling, with the exception of 1 and 3, which adopt the typical paddle-wheel structure of copper acetate and are thus strongly coupled.     

Preparation and structure of three solvatomorphs of the polymer [Co(dbm)2(4ptz)]n: spin canting depending on the supramolecular organization

The syntheses and X-ray structures of three isomeric 1D coordination polymers are reported. The complex [Co(dbm)2(MeOH)2] (1) was used as a precursor in these reactions. The preparation and structure of 1 is also presented; this mononuclear complex is in the cis configuration because this allows the formation of a network of intermolecular hydrogen bonds in the solid state. Reaction of 1 with 2,4,6-tris-(4-pyridyl)-1,3,5-triazine (4ptz) yields the polymers [Co(dbm)2(4ptz)]n.nTHF (2a), [Co(dbm)2(4ptz)]n.0.75nTHF.0.5nEt2O (2b), and [Co(dbm)2(4ptz)]n.3nDMF (2c) in the form of zigzag chains, instead of the expected honeycomb architectures. This is because of the establishment of extended pi-pi stacking throughout these solids, which could not have occurred otherwise. Compounds 2a, 2b, and 2c are solvatomorphs, and formation of either one of them depends on the exact conditions of crystallization, which lead to significant differences in the supramolecular organization of the chains. Bulk magnetic measurements on 2a reveal weak antiferromagnetic exchange within the chains and small ordering throughout the solid that results in the manifestation of the phenomenon of spin canting, whereas for 2c the different supramolecular organization causes the antiferromagnetic exchange not to result in spin canting.     

Synthesis,Characterisation, and in vitro Cytotoxic Activity of Dithiocarbamato Glycoconjugate Half-Sandwich Ruthenium and Osmium Complexes

The synthesis by transmetallation and in-depth characterisation by IR spectroscopy of five half-sandwich ruthenium and osmium dithiocarbamato isonipecotamide glycoconjugate complexes are presented herein. The evaluation of their in vitro cytotoxicity and of the zinc precursors’ in vitro cytotoxicity towards ovarian cancer (A2780 and A2780cisR) and normal prostate (PNT2) cells is reported. While the cytotoxicity of the compounds is rather limited, some selectivity is observed.